1. Field of the Invention
The present invention relates to an improvement of an on-vehicle electronic control device suitable for detecting fuel evaporation from a fuel tank in a parked state, measuring parking time, or the like.
2. Description of the Related Art
There are various known electronic control devices to which electric power is supplied from a battery mounted on a vehicle in an unmanned and parked state. They are used for detecting whether or not vapor generated in a fuel tank for an internal combustion engine mounted on a vehicle leaks to the outside of the fuel tank, for detecting whether or not a temperature sensor for cooling water for an internal combustion engine detects a decrease in water temperature as time passes after an engine stops, and/or for monitoring a state of a parked vehicle and performing blinking warning display as a part of functions of vehicle antitheft control.
For instance, there is provided an electronic control device performing control with the use of electric power supplied from a battery when a power switch is turned on (see paragraphs [0003] to [0005] and FIG. 1 of JP 2003-315474 A (hereinafter referred to as Patent Document 1), for instance). Patent Document 1 discloses a concept of a soak timer for detecting parked time for preheat control of cooling water or detection of fuel evaporation, which measures the parked time in appropriate measuring time and measuring accuracy for an application as a wide range specification.
According to Patent Document 1, a soak timer IC keeps time in a parked state where the power switch of a vehicle is opened, and after a predetermined period of time a power supply relay is driven to activate a host microcomputer as an engine control device. The host microcomputer performs predetermined control and then issues an instruction about the next activation to the soak timer IC. Then, the host microcomputer stops its action, and the power supply relay is turned off.
However, the soak timer IC can receive an instruction for selecting a clock unit and an instruction for activation clock time from the host microcomputer when the power switch is closed, but does not have a function of detecting fuel evaporation on by itself. In other words, presence or absence of fuel evaporation and/or an abnormal state of a water temperature sensor are detected by the host microcomputer itself as the engine control device while the soak timer IC is an IC only for keeping time.
In addition, there is provided an electronic control device for a vehicle, which is used for preventing a battery from being exhausted due to activation of an on-vehicle device while the engine is stopped (see paragraph [0017], Abstract, and FIG. 1 of JP 2003-232250 A (hereinafter referred to as Patent Document 2), for instance). In this electronic control device for a vehicle, the microcomputer as the engine control device is supplied with electric power from the on-vehicle battery via a power supply relay with a self holding action when the power switch is closed, and includes a timer function for keeping parked time after the power switch is opened. The microcomputer checks an abnormal state at the time point when a predetermined parked time has passed, and then turns off the power supply relay.
This electronic control device for a vehicle does not need a special IC for keeping the parked time. When discharge current of the on-vehicle battery increases after the power switch is opened so that the engine stops, the electronic control device measures discharging capacity of the on-vehicle battery in advance and then judges whether or not to keep the parked time.
In addition, there is provided a failure diagnosis apparatus for engine temperature sensing means, which can check a failure of the water temperature sensor for sensing cooling water temperature for the engine accurately and in early timing after the start of the engine (see paragraph [0026], Abstract, and FIG. 1 of JP 2000-282930 A (hereinafter referred to as Patent Document 3), for instance).
According to Patent Document 3, the engine control device includes a soak timer for detecting stop time of the engine, so as to keep parking time after the power switch is opened until it is closed again. By observing a change in cooling water temperature along with the parking time, the presence or absence of an abnormal state of the water temperature sensor is determined. Further, the action of the engine control device is stopped when the power switch is opened, but the soak timer works to keep the parking time with low power consumption by a backup voltage supplied continuously after the power switch is opened.
On the contrary, as a technique related to the present invention, there is a known electronic control device installed in a vehicle, which includes a main CPU and a sub CPU. In this on-vehicle electronic control device, the sub CPU and the main CPU cooperate with each other and work in parallel, whereby the sub CPU performs an assistant job such as bearing a part of an input and output control function or monitoring presence or absence of an abnormal state of the main CPU or an input and output circuit (see Abstract and FIG. 1 of JP 2002-089351 A (hereinafter referred to as Patent Document 4), for instance).
According to this on-vehicle electronic control device, an input signal for low speed operation is supplied to the sub CPU that is connected to the main CPU via a serial interface, and the input signal information is transmitted to the main CPU via a serial communication circuit. In addition, an output circuit for low speed operation is connected to the sub CPU, and the output circuit responds to an output control signal transmitted from the main CPU via the serial communication circuit. As a result, the number of input and output ports of the main CPU can be reduced, an input filter constant can be adjusted or set by the sub CPU, or other various assistant jobs can be performed by the sub CPU.
In addition, there is provided an air intake amount control device for an engine, having a duplexed CPU system for control (see Abstract and FIG. 1 of JP 2002-371897 A (hereinafter referred to as Patent Document 5), for instance). According to this air intake amount control device for an engine, a sub CPU is connected via a serial interface to a main CPU having a throttle valve opening degree control function and an engine control function. The sub CPU cooperates with the main CPU so as to detect an abnormal state of control, to stop power supply to a motor for controlling the throttle valve opening degree when an abnormal state occurs, to perform abnormal state warning display or to bear other various assistant functions.
The electronic control device disclosed in Patent Document 1 described above includes an external oscillator having high accuracy, and a reference clock is generated based on an oscillation signal of the oscillator. The reference clock signal is counted for keeping the parked time. It is not discussed in Patent Document 1 that an oscillator of low power consumption, low cost and low accuracy is utilized effectively. Therefore, the electronic control device has a drawback in that power consumption of the on-vehicle battery increases when the power switch is opened.
In addition, the soak timer IC is merely for keeping the parked time and does not have a fuel evaporation detecting function. Therefore, the host microcomputer is required to be supplied with electric power so as to perform the fuel evaporation detection control action when the power switch is closed. Consequently, power consumption of the on-vehicle battery increases when the power switch is opened.
In addition, the device described in the above-mentioned Patent Document 2 does not perform control of power consumption of the on-vehicle battery in the parked state without being charged. Therefore, there arises a problem that set time of the timer for keeping the parked time is restricted or that the parked state cannot be monitored in order to prevent the on-vehicle battery from being in the over discharged state.
Further, in general, a timer circuit commonly called a soak timer keeps a lapse time after the power switch is closed and supplies electric power temporarily to the control device so as to activate a microprocessor when a predetermined period of time passes, whereby the microprocessor can perform short time measuring and monitoring control before turning off the power. Such the intermittent activation is repeated a plurality of times. Therefore, even if the activated operation ends in short time, there arises a problem that the activation of the microprocessor with high speed and large memory capacity can be a large load on the on-vehicle battery while the battery is not charged.
In addition, the device described in the above Patent Document 3 does not have a vehicle monitoring function during the parked state and is limited to the function of merely keeping the parking time after the power switch is opened until it is closed again. Therefore, there arises a problem monitoring control of the fuel evaporation detection cannot be performed during a period while the power switch is opened.
In addition, the devices described in the above Patent Documents 4 and 5 do not relate to the parked state monitoring after the power switch is opened, and the sub CPU is in the disabled state when the power switch is opened. Therefore, there arises a problem that the monitoring control of the fuel evaporation detection cannot be performed during the period while the power switch is opened.